Grease Pencil looks different rendered then in viewport with opaque materials #60538

Closed
opened 2019-01-15 16:48:16 +01:00 by Steve Lund · 21 comments

System Information
Operating system: Win 10
Graphics card: 1080 Ti

Blender Version

blender2.8, 2019-01-14

Worked: (optional)

Grease Pencil looks very different rendered when using semi-transparent materials, tested using both Filmic and Default Color profiles. Only way to fix is by adding an additional layer and making it completely white.

Exact steps for others to reproduce the error
Draw in Grease Pencil with semi-transparent pink filled material. And compare rendered result to viewport.

**System Information** Operating system: Win 10 Graphics card: 1080 Ti **Blender Version** blender2.8, 2019-01-14 Worked: (optional) Grease Pencil looks very different rendered when using semi-transparent materials, tested using both Filmic and Default Color profiles. Only way to fix is by adding an additional layer and making it completely white. **Exact steps for others to reproduce the error** Draw in Grease Pencil with semi-transparent pink filled material. And compare rendered result to viewport.
Author

Added subscriber: @SteveLund

Added subscriber: @SteveLund
Member

Added subscriber: @JacquesLucke

Added subscriber: @JacquesLucke
Member

Could you provide an example .blend file, please?

Could you provide an example .blend file, please?
Author

GreasePencil_bug.blend Just simply render and compare to the rendered viewport.

[GreasePencil_bug.blend](https://archive.blender.org/developer/F6296623/GreasePencil_bug.blend) Just simply render and compare to the rendered viewport.
Member

Screenshot from 2019-01-15 16-59-24.png

![Screenshot from 2019-01-15 16-59-24.png](https://archive.blender.org/developer/F6296673/Screenshot_from_2019-01-15_16-59-24.png)
Antonio Vazquez was assigned by Brecht Van Lommel 2019-01-15 17:03:05 +01:00

I have been looking at your file and there are some parameters that need to be chnaged.

The first is you are using a world color taht is different of the viewport, so as the background is different, the transparent looks different.

The second issue is that you need to change the color manamegement.

Attached the file fixed. I have added a white background to test with the same background.GreasePencil_bug_changed.blend

I have been looking at your file and there are some parameters that need to be chnaged. The first is you are using a world color taht is different of the viewport, so as the background is different, the transparent looks different. The second issue is that you need to change the color manamegement. Attached the file fixed. I have added a white background to test with the same background.[GreasePencil_bug_changed.blend](https://archive.blender.org/developer/F6304565/GreasePencil_bug_changed.blend)
Author

Hey Antonio!

Changing the color management and making the world color for the view-port background white doesn't fix the transparent issues.

The only thing that has fixed the transparent issues that I've found (and like you have done in the example.) Is adding a new completely white plane to the background.

This seems like a work-around though? and shouldn't be the default as it would be confusing for beginners to have their renders looking much different then the view-port right?

Hey Antonio! Changing the color management and making the world color for the view-port background white doesn't fix the transparent issues. The only thing that has fixed the transparent issues that I've found (and like you have done in the example.) Is adding a new completely white plane to the background. This seems like a work-around though? and shouldn't be the default as it would be confusing for beginners to have their renders looking much different then the view-port right?

Added subscriber: @intracube

Added subscriber: @intracube

Hi,

With the viewport set to Rendered, the output still gives different results:
grease_pencil_mixed_alpha_blending.png

It looks like the viewport is doing an unassociated alpha blend with the background but the final render is associated/premultiplied.

Manually filling a background GP layer is a workaround but not all that ideal. The second .blend also shows issues along the rectangle edges:
grease_pencil_mixed_alpha_blending_box_edge.png

The rectangle could be expanded beyond the edges of the frame of course. But the user has to know to do it.

Could an unassociated->premultiplied transform be inserted for the final render out? My brain can't work out the details, but I'm thinking that should be possible?

Hi, With the viewport set to Rendered, the output still gives different results: ![grease_pencil_mixed_alpha_blending.png](https://archive.blender.org/developer/F6307911/grease_pencil_mixed_alpha_blending.png) It looks like the viewport is doing an unassociated alpha blend with the background but the final render is associated/premultiplied. Manually filling a background GP layer is a workaround but not all that ideal. The second .blend also shows issues along the rectangle edges: ![grease_pencil_mixed_alpha_blending_box_edge.png](https://archive.blender.org/developer/F6307922/grease_pencil_mixed_alpha_blending_box_edge.png) The rectangle could be expanded beyond the edges of the frame of course. But the user has to know to do it. Could an unassociated->premultiplied transform be inserted for the final render out? My brain can't work out the details, but I'm thinking that should be possible?

I know that adding a white background is not the perfect solution, but manage the background color will be part of the Eevee integration with Grease Pencil, but this integration is not ready (not in 2.80) and will be implemented in future versions.

I know that adding a white background is not the perfect solution, but manage the background color will be part of the Eevee integration with Grease Pencil, but this integration is not ready (not in 2.80) and will be implemented in future versions.

Added subscriber: @troy_s

Added subscriber: @troy_s

It’s Blender’s broken alpha handling. Has been this way forever, and the “fixes” that were added broke it at least as bad. And the viewer is broken.

It’s give up until a developer decides to fix the entire pipeline to associated alpha.

To see the proper result, broken viewer notwithstanding, paint in float. The reason that it works in float is because the float path didn’t decide to break the entire pipeline by supporting unassociated alpha.

It’s Blender’s broken alpha handling. Has been this way forever, and the “fixes” that were added broke it at least as bad. And the viewer is broken. It’s give up until a developer decides to fix the entire pipeline to associated alpha. To see the proper result, broken viewer notwithstanding, paint in float. The reason that it works in float is because the float path didn’t decide to break the entire pipeline by supporting unassociated alpha.

Yes, this needs a fix, but it's not only in grease pencil, so it needs developers in other areas the Blender and currently there aren't resources to do it.

Yes, this needs a fix, but it's not only in grease pencil, so it needs developers in other areas the Blender and currently there aren't resources to do it.

Added subscriber: @brecht

Added subscriber: @brecht

Changed status from 'Open' to: 'Resolved'

Changed status from 'Open' to: 'Resolved'

This appears to be fixed now.

This appears to be fixed now.

There's now quite a hue error for semi-transparent objects:
buildbot_2019-06-07_greasepencil_viewport_vs_render_difference_01.png

Tested with today's (2019-06-07) buildbot release: aa003c73245f-linux-glibc224-x86_64

Same results with a build from Feb 21st, so not a recent change.

Stroke:
[0.999828, 0.315918, 0.000000, 1.000000]

Fill:
[0.999828, 0.522433, 0.000000, 0.253246]

Color Management: defaults

There's now quite a hue error for semi-transparent objects: ![buildbot_2019-06-07_greasepencil_viewport_vs_render_difference_01.png](https://archive.blender.org/developer/F7092258/buildbot_2019-06-07_greasepencil_viewport_vs_render_difference_01.png) Tested with today's (2019-06-07) buildbot release: aa003c73245f-linux-glibc224-x86_64 Same results with a build from Feb 21st, so not a recent change. Stroke: [0.999828, 0.315918, 0.000000, 1.000000] Fill: [0.999828, 0.522433, 0.000000, 0.253246] Color Management: defaults

Changed status from 'Resolved' to: 'Open'

Changed status from 'Resolved' to: 'Open'

Just to add; if as before, a solid fill object is added to a background layer - the hue is normalised.

White rectangle added to the left side:
buildbot_2019-06-07_greasepencil_viewport_vs_render_difference_back_solid_fill.png

Just to add; if as before, a solid fill object is added to a background layer - the hue is normalised. White rectangle added to the left side: ![buildbot_2019-06-07_greasepencil_viewport_vs_render_difference_back_solid_fill.png](https://archive.blender.org/developer/F7092306/buildbot_2019-06-07_greasepencil_viewport_vs_render_difference_back_solid_fill.png)
Antonio Vazquez was unassigned by Dalai Felinto 2019-12-23 16:35:25 +01:00

Added subscriber: @antoniov

Added subscriber: @antoniov

Closed as duplicate of #66293

Closed as duplicate of #66293
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Reference: blender/blender#60538
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